# Australiformis

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Australiformis
> Markdown URL: https://mediated.wiki/source/Australiformis.md
> Source: https://en.wikipedia.org/wiki/Australiformis
> Source revision: 1324578260
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

***Australiformis*** is a [monotypic](/source/Monotypic_taxon) genus of [acanthocephalans](/source/Acanthocephala) (thorny-headed or spiny-headed [parasitic](/source/Parasitism) worms) containing a single species, ***Australiformis semoni***, that infests [marsupials](/source/Marsupials) in [Australia](/source/Australia) and [New Guinea](/source/New_Guinea). Its body consists of a [proboscis](/source/Proboscis) armed with hooks which it uses to pierce and hold the gut wall of its host, and a long trunk. This genus resembles species in the genus *[Moniliformis](/source/Moniliformis)* but is characterized by a lack of spiral muscles in the outer wall of the proboscis receptacle. The proboscis is armed with 12 rows of 13 to 15 hooks which are used to attach themselves to the small or large intestines of the host. The female worms range from 95 to 197 millimetres (3.7 to 7.8 in) long, virtually all of which is the trunk, and 1.75 to 3.5 millimetres (0.069 to 0.138 in) wide. There is pronounced [sexual dimorphism](/source/Sexual_dimorphism) in this species as females are around twice the size of the males whose trunks range from 46 to 80 millimetres (1.8 to 3.1 in) long and 2 millimetres (0.079 in) wide. Infestation by *A. semoni* may cause debilitating inflammation of the stomach ([gastritis](/source/Gastritis)) with [granulomatous](/source/Granulomatous) ulcers.

## Taxonomy

The taxonomic history of *A. semoni* is complex. It was originally named *Echinorhynchus semoni* by [Linstow](/source/Otto_Friedrich_Bernhard_von_Linstow) in 1898,[2] and then moved to *Gigantorhynchus* by Porta in 1908[3] and Johnston in 1909, later moved to *Prosthenorchis* by Travassos in 1917,[4] then renamed *Moniliformis semoni* by Johnston and Edmonds in 1952[5] before taking the present name and genus by Schmidt and Edmonds in 1989.[6][1] The genus is [monotypic](/source/Monotypic), the only species, *Australiformis semoni* (Linstow, 1898)[a], being necessarily the [type species](/source/Type_species).[7] Linstow named the species *semoni* after the German zoologist who discovered it, [Richard Semon](/source/Richard_Semon).[2]

The [morphological](/source/Morphology_(biology)) traits of a simple, double-walled [proboscis](/source/Proboscis) receptacle, eight cement glands (which are used to temporarily close the posterior end of the female after copulation) each with a giant nucleus, the brain at the posterior end of proboscis receptacle, and dorsal and ventral lacunar canals place this genus confidently in the order [Moniliformida](/source/Moniliformida). The genus *Australiformis* Schmidt and Edmonds, 1989 was created for *Moniliformis semoni* as this species differed from other species in *[Moniliformis](/source/Moniliformis)* and the other genera of the family Moniliformidae, *[Promoniliformis](/source/Promoniliformis)*, because it lacked spiral muscles in the outer wall of the proboscis receptacle. The parasitizing of marsupials is also a unique trait of this genus among Acanthocephala.[1] The [National Center for Biotechnology Information](/source/National_Center_for_Biotechnology_Information) does not indicate that any [phylogenetic](/source/Phylogenetic) analysis has been published on *Australiformis* that would confirm its position as a unique genus in the family Moniliformidae.[8]

## Description

Anatomical measurements of A. semoni Measurements[1] Female (mm) Male (mm) Length of proboscis 0.640–0.800 0.600–0.840 Width of proboscis 0.280–0.320 0.200–0.288 Length of proboscis receptacle 1.2–1.58 1.0–1.7 Width of proboscis receptacle 0.3–0.48 0.32–0.36 Length of neck 0.225–0.240 0.150–0.240 Width of neck at base 0.200–0.270 0.200–0.270 Length of trunk 95–197 46–80 Width of trunk 1.75–3.5 2 Length of lemnisci 25–27 20–25 Size of anterior testis 2.7–3.2 x 0.75–1.0 Size of posterior testis 2.5–3.2 x 0.75–1.0 Size of cement glands 0.64–1.2 x 0.44–0.72 Size of Saefftigen's pouch 1.28 x 0.48–0.64 Size of eggs 0.080–0.086 x 0.035–0.044 Distance from the uterine bell[b] to genital pore 1.95–2.2

*A. semoni* consists of a proboscis covered in hooks, a proboscis receptacle, and a long trunk. There is pronounced [sexual dimorphism](/source/Sexual_dimorphism) in this species; the females are around twice as long as the males (up to approximately 20 centimetres (7.9 in) in females and 8 centimetres (3.1 in) in males). The proboscis is long and swollen at the [anterior](https://en.wiktionary.org/wiki/anterior) end and tapers rapidly to a narrow base. The proboscis is armed with 12 rows of 13 to 15 hooks. The first three to four hooks in each row are large, aligned in straight rows, and have [bifid](https://en.wiktionary.org/wiki/bifid) roots whereas the other 10 to 12 posterior hooks are small rootless spines arranged in spirals down the proboscis. The first hook of each row is 40 to 56 micrometres (0.0016 to 0.0022 in) long, the second is 50 to 60 micrometres (0.0020 to 0.0024 in) long, the third is 42 to 50 micrometres (0.0017 to 0.0020 in) long, the fourth is 42 to 54 micrometres (0.0017 to 0.0021 in) long and the remaining spines are 30 to 60 micrometres (0.0012 to 0.0024 in) long. At the base of the proboscis is a double-walled proboscis receptacle with a smooth outer wall, lacking spirally arranged muscle fibers, and a large space between the walls. The brain is located near the posterior end of the proboscis receptacle with [retinacula](/source/Retinaculum) (a band of thickened [deep fascia](/source/Deep_fascia) around [tendons](/source/Tendon) that holds them in place) piercing the proboscis receptacle wall laterally. Proboscis retractor muscles pierce the posterior end of the proboscis receptacle.[1]

The trunk is not [pseudosegmented](/source/Segmentation_(biology)), is very thin at the anterior end and thickest at the posterior end averaging only a few millimeters in width. The main [longitudinal](https://en.wiktionary.org/wiki/longitudinal) [lacunar](https://en.wiktionary.org/wiki/lacuna) canals are [dorsal](https://en.wiktionary.org/wiki/dorsal) and [ventral](https://en.wiktionary.org/wiki/ventral), with the dorsal canal being conspicuous and the ventral canal being very narrow. The [transverse](https://en.wiktionary.org/wiki/transverse) [commissural](/source/Commissure) canals are evenly spaced and connect to the main longitudinal canals. The [lemnisci](/source/Lemniscus_(anatomy)) (bundles of sensory nerve fibers) are long, slender, twisted, and coiled in the body cavity (not attached distally to the body wall), and contain 10 to 15 giant nuclei each. They extend between one quarter to one third the length of the body.[1]

The eggs are oval with three apparent membranes. The outer membrane is thick with the exception of the anterior end where it is thin. The outer membrane is often indented and the posterior end is usually covered in small dots on the outer surface with a knob on the inner surface. The second membrane is very thin and the third membrane is thick. The males have a sensory pore on each side of the neck. Males have eight oval cement glands, each with a single giant nucleus, and possess a [Saefftigen's pouch](/source/Saefftigen's_pouch) just behind the [testes](/source/Testes).[1] The testes are oval in tandem and found near the posterior end of the trunk. The genital pore is located at the terminal end of the trunk in both sexes.[1]

## Distribution

The distribution of *A. semoni* is determined by that of its hosts. *A. semoni* has been found in several states of Australia, including [Queensland](/source/Queensland), [New South Wales](/source/New_South_Wales), and [Tasmania](/source/Tasmania). This parasite has also been found in [Boroko](/source/Boroko), Papua New Guinea. The [type locality](/source/Type_(biology)) is the Upper [Burnett River](/source/Burnett_River) region in south-eastern Queensland.[1]

## Hosts

The life cycle of an acanthocephalan consists of three stages beginning when an infective acanthor (development of an egg) is released from the intestines of the [definitive host](/source/Host_(biology)#Types_of_hosts) and then ingested by an arthropod, the [intermediate host](/source/Host_(biology)#Types_of_hosts). Although the intermediate hosts of *Australiformis* are not known, without exception for the order [Moniliformida](/source/Moniliformida), this intermediate host is an insect. When the acanthor [molts](/source/Molt), the second stage called the acanthella begins. This stage involves penetrating the wall of the [mesenteron](/source/Mesenteron) or the intestine of the intermediate host and growing. The final stage is the infective cystacanth which is the [larval](/source/Larva) or juvenile state of an Acanthocephalan, differing from the adult only in size and stage of sexual development. The cystacanths within the intermediate hosts are consumed by the definitive host, usually attaching to the walls of the intestines, and as adults they reproduce sexually in the intestines. The acanthor are passed in the [feces](/source/Feces) of the definitive host and the cycle repeats. There are no known [paratenic hosts](/source/Host_(biology)#Types_of_hosts) (hosts where parasites infest but do not undergo larval development or sexual reproduction) for *Australiformis*.[9]

*A. semoni* parasitizes Australian and [New Guinean](/source/New_Guinea) marsupials including the [type host](/source/Type_host), [southern brown bandicoot](/source/Southern_brown_bandicoot) (*Isoodon obesulus*) and related species such as the [northern brown bandicoot](/source/Northern_brown_bandicoot) (*Isoodon macrourus*), [long-nosed bandicoot](/source/Long-nosed_bandicoot) (*Perameles nasuta*), [striped bandicoot](/source/Striped_bandicoot) (*Perameles gunnii*), [common echymipera](/source/Common_echymipera) (*Echymipera kalubu*), and [brush-tailed phascogale](/source/Brush-tailed_phascogale) (*Phascogale tapoatafa*). *A. semoni* infests these hosts by using hooks on their proboscis to pierce and hold the wall of the small and large intestines.[1] *A. semoni* has also been found with the anterior end embedded in the mucosa of the stomach in the striped bandicoot. This infestation, which all observed cases contained 5 or fewer individual worms, may cause debilitating ulcerative granulomatous gastritis, a form of [gastritis](/source/Gastritis) (inflammation of the stomach) characterised by [ulcers](/source/Ulcer) and [granuloma](/source/Granuloma) (an aggregation of [macrophages](/source/Macrophage) that forms in response to chronic [inflammation](/source/Inflammation)).[10] Juvenile worms were found in the [accidental host](/source/Host_(biology)#Types_of_hosts) (an organism that generally does not allow transmission to the definitive host) [brown antechinus](/source/Brown_antechinus) (*Antechinus stuartii*).[1] There are no reported cases of *A. semoni* infesting humans in the English language medical literature.[11]

## Notes

1. A [binomial authority](/source/Binomial_nomenclature) in parentheses indicates that the species was originally described in a genus other than *Australiformis*.

1. a funnel like opening continuous with the uterus.

## References

1. Schmidt, G.D. & Edmonds, S.J. (1989). "*Australiformis semoni* (Linstow, 1898) n. gen., n. comb. (Acanthocephala: Moniliformidae) from marsupials of Australia and New Guinea". *The Journal of Parasitology*. **75** (2): 215–7. [doi:10.2307/3282769](https://doi.org/10.2307/3282769). [JSTOR 3282769](https://www.jstor.org/stable/3282769). [PMID 2926590](https://pubmed.ncbi.nlm.nih.gov/2926590)

1. von Linstow, O.F.B. (1898). ["Nemathelminthen von Herrn Richard Semon in Australien gesammelt"](https://archive.org/details/bub_gb_uRRFAQAAIAAJ) (in German). *Denkschriften der Medizinisch-Naturwissenschaftlichen Gesellschaft zu Jena*. **8**: [471–472](https://archive.org/details/bub_gb_uRRFAQAAIAAJ/page/n458). Retrieved March 23, 2020.

1. Porta, A. (1908). "Gli acantocefali dei mammiferi. Noto preventiva". *Archives de parasitologie*. **12** (2): 268–282.

1. Travassos, L. (1917). "Contribuigoes para o conhecimento da fauna helmintolojica brazileira. VI. Revisao dos acantocefalos brazileiros. Parte l. Fam. Gigantorhynchidae Hamann, 1892" (in Portuguese). *Memórias do Instituto Oswaldo Cruz*. **9**: 5–62. [doi:10.1590/S0074-02761917000100001](https://doi.org/10.1590/S0074-02761917000100001)

1. Johnston, T.H. & Edmonds, S.J. (1952). ["Australian Acanthocephala No. 9"](https://www.biodiversitylibrary.org/part/82177). *Transactions of the Royal Society of South Australia*. **75**: 16–21. [Archived](https://web.archive.org/web/20230321153704/https://www.biodiversitylibrary.org/part/82177) 21 March 2023 at the Wayback Machine. Retrieved 21 March 2023.

1. ["Moniliformida Schmidt, 1972"](https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=196572). *Integrated Taxonomic Information System (ITIS)*. November 23, 2019. [Archived](https://web.archive.org/web/20230503234106/https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=196572) 3 May 2023 at the Wayback Machine. Retrieved January 30, 2020.

1. Amin, O.M. (September 19, 2013). "Classification of the Acanthocephala". *Folia Parasitologica*. **60** (4): 273–305. [doi:10.14411/fp.2013.031](https://doi.org/10.14411/fp.2013.031). [PMID 24261131](https://pubmed.ncbi.nlm.nih.gov/24261131)

1. Schoch, Conrad L; Ciufo, Stacy; Domrachev, Mikhail; Hotton, Carol L; Kannan, Sivakumar; Khovanskaya, Rogneda; Leipe, Detlef; Mcveigh, Richard; O’Neill, Kathleen; Robbertse, Barbara; Sharma, Shobha; Soussov, Vladimir; Sullivan, John P; Sun, Lu; Turner, Seán; Karsch-Mizrachi, Ilene (2020). ["NCBI Taxonomy: a comprehensive update on curation, resources and tools."](https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=60528). *Database*. [doi:10.1093/database/baaa062](https://doi.org/10.1093/database/baaa062). [PMC 7408187](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7408187). [PMID 32761142](https://pubmed.ncbi.nlm.nih.gov/32761142). Retrieved April 1, 2024.

1. Schmidt, G.D. (1985). ["Development and life cycles"](https://core.ac.uk/download/pdf/17218255.pdf). *Biology of the Acanthocephala*. Crompton, D.W.T. & Nickol, B.B. (eds.). Cambridge: Cambridge Univ. Press. pp. 273–305. [Archived](https://web.archive.org/web/20230722191034/https://core.ac.uk/download/pdf/17218255.pdf) 22 July 2023 at the Wayback Machine. Retrieved 16 July 2023.

1. Lenhaus, C.; Obendorf, D.; Wright, F.H. (1990). ["Veterinary aspects of *Perameles gunnii* biology with special reference to species conservation"](https://www.researchgate.net/publication/258341847). *Management and conservation of small populations*. Clark, T.W. & Seebeck, J.H. (eds.). Brookfield, Illinois: Chicago Zoological Society. pp. 89–108. ISBN 0-913934-16-X. Retrieved March 23, 2020.

1. Mathison, BA et al. (2021). ["Human Acanthocephaliasis: a Thorn in the Side of Parasite Diagnostics"](https://doi.org/10.1128%2FJCM.02691-20). *J Clin Microbiol*. **59** (11): e02691-20. [doi:10.1128/JCM.02691-20](https://doi.org/10.1128/JCM.02691-20). [PMC 8525584](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8525584). [PMID 34076470](https://pubmed.ncbi.nlm.nih.gov/34076470)

---
Adapted from the Wikipedia article [Australiformis](https://en.wikipedia.org/wiki/Australiformis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Australiformis?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.